This invention relates to a back spacing apparatus for a tape player for use with a dictating transcriber machine, in which a tape is automatically rewound a predetermined amount for back spacing when the player is switched from a reproduce mode to a stop mode.
When information recorded on a tape is transcribed, if there is a passage difficult to catch or follow, it is necessary to first stop the tape and then listen to it again by rewinding the tape to some extent and reproducing it. It is therefore necessary for the typist to effect the rewinding and playback operations of the tape each time any passage difficult to catch is encountered. Such a cumbersome operation is required in a case where typing, once interrupted for urgent business, is continued.
In order to solve the above-mentioned inconvenience a back spacing apparatus for automatically rewinding a tape is currently used. For example, Japanese Patent publication No. 11211/77 or Japanese Patent Disclosure No. 71304/75 discloses a technique relating to such a back spacing apparatus. It is desirable that an amount of memory contents on that portion of a recorded tape rewound for back spacing be made substantially constant irrespective of the tape running or transporting speed at the time of playback. For a tape speed of either 2.4 cm/s or 1.2 cm/s it is desirable that a length of a tape over which it is rewound for back spacing correspond to about one to two words (one to three seconds) of a normal conversation. In the conventional back spacing apparatus, however, no particular consideration is paid to the rewinding of the tape over a predetermined length with respect to a change in tape speed. That is, in the conventional back spacing apparatus the tape is rewound a fixed amount for back spacing irrespective of the tape transporting speed. For this reason, an amount of memory contents on that portion of a recorded tape rewound for back spacing varies dependent upon the speed at which the tape is recorded. Suppose, for example, that use is made of an apparatus adapted to rewind a recorded tape amount corresponding to a playback time of 2 seconds at a tape speed of 2.4 cm/s so as to present a corresponding amount of memory contents on the recorded tape.
In this case, if a tape is recorded at a speed of 1.2 cm/s it follows that the recorded tape is rewound for back spacing so as to present those memory contents on the recorded tape which correspond to about 4 seconds. The longer the time during which said memory contents are reproduced, the lower the typing efficiency. In an apparatus adapted to rewind a recorded tape for back spacing so as to present an amount of memory contents on the recorded tape corresponding to 2 seconds at a tape speed of 1.2 cm/s, it follows that the tape is rewound an amount corresponding to only one second for back spacing, compared with the case where the tape speed is 2.4 cm/s. In this case, the head or beginning of the backspaced word tends to be mutilated since a length of the tape over which the tape is so rewound is insufficient.